Mattresses used in cribs for infants have conventionally resembled adult mattresses built to a smaller scale. For various reasons, however, the requirements of a crib mattress are different than what is required for adult sized mattresses, such as single, twin, queen and king sizes. For example, the weight of an infant is so much less than the weight of an adult that a regular mattress simply built to a smaller scale is too stiff and unyielding for a recumbent infant. Mattress designs that provide additional edge support to compensate for the effects of people sitting on the edge of their beds actually detract from the quality of a crib mattress. Fitting within the side bars or walls of a crib is another requirement that is not critical for an adult sized mattress that simply sits on top of a box spring.
A stiff crib mattress cannot be forced to fit inside the crib if the mattress is too large. Even a conventional foam mattress, as opposed to an innerspring mattress, that is too large will bulge if the mattress is forced into a crib with smaller dimensions. Thus, crib mattresses are typically manufactured to be smaller than the standard crib size in order to provide some tolerance to compensate for variations in manufacturing processes of the crib and the mattress. For example, sizes vary even among individual cribs of the same model manufactured by the same company. Sizes of individual mattresses also vary even among the same model of crib mattress manufactured by the same company. Thus, to ensure that a crib mattress fits any particular crib, the typical conventional crib mattress can be a couple of inches too short and too narrow.
FIG. 1 (prior art) shows a conventional crib assembly 10 including a crib 11 and an infant mattress 12. The outer dimensions of infant mattress 12 are smaller than the inner dimensions of the bars 13 that form a frame around the mattress. Consequently, there is a gap 14 between the edges 15 of mattress 12 and bars 13. Gap 14 is dangerous because an infant could become trapped in gap 14 between mattress 12 and bars 13. The baby's hands, legs or even head could become wedged between crib 11 and ill fitting mattress 12.
FIG. 2 (prior art) shows a conventional way of trying to prevent an infant from becoming trapped between an ill fitting infant mattress and the crib. Crib assembly 16 includes crib 11, infant mattress 12 and a bumper assembly 17. Bumper assembly 17 can be made of four connected side pieces that fit around the inside edges of crib 11 above mattress 12. Bumper assembly 17 is intended to cover any gap between mattress 12 and bars 13. In addition, bumper assembly 17 covers bars 13 to a height that a recumbent infant is likely to reach. A twisting and turning infant, however, invariably manages to insert a limb under bumper assembly 17 that can become lodged between a bar of the crib 11 and mattress 12. In FIG. 2, an infant has lodged his left foot in a gap 14 between mattress 12 and a bar 18.
An infant mattress and a crib assembly are sought that prevent infants from becoming trapped between the mattress and a standard crib.